Greedy is a rather bland clone of the Snake game for the NES.
As with many Nice Code games, pressing Up, Down, Left, Right, holding A + B (pressing A before B) and pressing Right on the title screen will briefly display a credits screen. Nature Color Game is one of several aliases used by Nice Code, and PJ most likely refers to the Power Joy series of Famiclones which many Nice Code games have been released on.
One By One
An alternate version of this game exists which replaces the title screen and music, and disables the code to access the credits screen.